Hawkes and McLaurin specifically draw attention to the perivascular macrophage subset. They have performed two definitive in-vivo experiments to discern the functional role of these cells in the context of AD-like pathology in TgCRND8 mice: 1) they reduced numbers of perivascular macrophages using clodronate, and 2) increased turnover of these cells using chitin. Results from both experiments suggest that perivascular macrophages are an important class of Aβ phagocytes that serve to limit cerebral amyloid angiopathy. Interestingly, these cells were unable to migrate into the brain parenchyma, and instead were restricted to cerebral vessels. It will be important to further discern the signals necessary to promote both brain penetration of these cells and Aβ engulfment/clearance in the AD brain. Elucidation of these signals will likely lead to novel therapeutic targets for the human syndrome.